Cycloidal grinding and mixing device



Aug. 12, 1952 c, NEFF 2,606,721

CYCLOIDAL. GRINDING AND MIXING DEVICE Filed Dec. 31, 1948 W5 24 ,f I? 16- Patented Aug. 12, 1952 DEVIC Cole D. Nell, Buenos Aires, Argentina Application December 31, 1948, Serial No; 68,615

3 Claims. (01. 241-253) This invention relates to grinding and mixing devices .and more particularly to improvements in grinding and mixing devices wherein the material .to be treated is passed between rotating cycloidal rolls.

in the :past, ,kneading, dispersing, crushing, pulverizing, mixing and grinding have been accomplished by manydifierent types of machinery. Broadlyspeaking-such machinery falls into fivemain categories, first, is the mill stone-type; second, is the jaw crusher or hammer mill type; third,= is the gyratory crusher; fourth, is the roll mill; and fifth, is theball mill, either wetor dry. Themill stone has the obvious disadvantages-of being "inellicient to operate'and not productive of-auniform product. The jaw crusher is ineilicient in that 'itsworking' stroke represents only one half of its-movement, its reciprocating action causes considerable vibration rendering the power consumption uneven and the product inferior. The gyratory crusher is efficient as a primaryandsecondary crusher but cannot be used when it is desired to achievev a large reduction in' th'e size ofthe particles treated. Inaddition, the gyratory crusher gives a non-uniform product. The roll mill produces a comparatively uniform product, but loses eliiciency due to slippage between the rolls, and abrasive particles slipping at thebite between the rolls tend tocausegrooves which seriouslyshorten the effective llfeof the rolls. The roll mill-hasthe additional disadvantage of sometimes requiring-considerable re-circul-ation back through the rolls to obtain a uni crusherisibest :suited for primary crushing, the 1 rollmill for. granulating, and the ball mill for pulverizing. But hitherto no commercially successful grinder has been well adapted for these several types of grinding simultaneously.

Referring-now to the specific field of grinding machinery used in dispersing pigment into a vehicle, one extremely important limitation present in the conventional mill is that it operates intermittently, grinding only one batch ata time.

No mill has as yet been'designed which can adequatelyhandie dispersion of pigments by a continuous process. Another disadvantage .in conventional paint dispersion equipment involves the human element. Often highly skilled operators must be employed for the purpose making meticulous settings and governing the grinding time. Another disadvantage in the conventional pigment dispersing mill is the necessity of recirculating the pigment through the mill. Conventional paint dispersing mills also occupy considerable space, they are difficult to clean, and in-general. they require operation at substantial viscosity above the viscosity of the marketed paint-and thereby require more power consumption. Another disadvantage is seen in the necessity of pre-mixing, and intermediate paste storage before the final product is mixed. And finally, the conventional mills are expensive to operate, difficult to regulate with regard to quality and fineness, and are generally slow in the accomplishment of their object. 7

Therefore it is an object of-my invention to provide a machine for grinding and m'ixingwhich will at one and the same time be suitable :for preliminary grinding, for granulating, or' for pulveriz-ing. Another object of my invention is to provide such a machine which will, occupy relatively small space, be easy to clean, operate at high rate and low cost, and requirelittle human skill in its adjustment. Another object of my invention is to provide such amachin -which will be capable of grinding and mixing'by, continuous process. A further object of my invention is to provide a paint'dispersing mill which will disperse pigment without the necessity of pre-mixing, and which will operatesatisfactorily at the viscosity of the marketable product. ,An additional object of my invention is to provide a grinding or mixing mill in which the material to be treated can be passed repetitively between'the grinding surfaces without the necessity 0f recirculation, and a mill in which the number of such passages can be controlled.

In order to accomplish these o-bjects, I employ in a preferred embodiment of myinvention-two axially aligned identical'cycloidal rolls. These rolls are placed alongside each other separated only by the desired grinding clearanceand-with the epicycloid (convex portion) of one-rollfitting into the hypccycloid (concave'portion) of the Other.

Another "feature of my invention resides in cycloidal rolls having tapered upper portionsgfor' use inacontinuous process mill, and in "addition a chamber separated from such tapered rolls only by the desired grinding clearance. With this arrangement the number of passages between the rolls made by each particle can be controlled by regulating the rotational velocity of the rolls.

Further objects and features of my invention will best beunderstood and appreciated by reference to a detailed description of a preferred embodiment selected for the purposes of illustration and shown in the accompanying drawings in which:

Figure 1 is a view in cross section of the mill of my invention designed for continuous operation;

Figure 2 is a view in front elevation of the mill of my invention designed for continuous operation with part of the exterior wall broken away to expose the grinding chamber;

Figure 3 is a View in side elevation of the same. The preferred embodiment of my invention as herein shown, may be adapted for use in a continuous grinding or mixing process.

The machine adapted for continuous process operation is shown in Figures 1-3 inclusive, and comprises a base I which supports a tube-like shell I I, the walls of which are massive and may be'composed of steel or other suitably obdurate substance. The shell II is oval in cross section, and, internally, it is machined to form two intersecting, hollow, vertical cylinders which comprise a grinding chamber I2. The tube II is provided witha top plate I4.

Within the grinding chamber I2, two cycloidal grinding rolls I6 having tapered upper ends are mounted on shafts I! which in turn are supported for axial rotation by the bearings I8 located in the base I 0 and the top plate I4. The rolls I6 are cycloidal in cross-section, their curves being generated by the same generating circle upon the same base circle with the circumference of the generating circle being aneven mult ple (except uniw) of the base circle, the base circles of the tworolls being equal and tangent. The rolls I Shave axes which are parallel to each other, and are arran ed with the epicycloid (convex portion) of one roll fitting into the hypocycloid (concave portion) of the other, and being separated at the straight portion of their bodies, below the tapered portion, only by the desired grinding clearance. The shafts I! are mounted respectively concentrically within the intersecting hollow cylindrical portions of the chamber I2 and the rolls I6 are dimensioned so that the epicycloidal surface likewise clears the walls of the said chamber I2 only by the desired grinding clearance. Thus it will be seen that the radius of the hollow cylinders forming the grinding chamber I2, is the radius of the circle subtended by the epicycloid of the rolls plus the grinding clearance, and that the axis of shafts l1 (and consequently the hollow cylinders) must be spaced apart a distance equal to the radius of the circle subtended by the epicycloid plus that of thehypocycloid, plus the grinding clearance.

I The shafts I! are provided with gears 20 located at both ends of each shaft II, which gears intermesh and serve to drive the rolls at equal peripheral speeds in opposit directions. At the top of the grinding chamber I2, but below the upper gears 20, a partition wall 24 is provided for the purpose of preventing the material being treated from impeding the upper gears 20. A pulley 2I is secured to one of the shafts I1 and, being connected to a suitable source of power, drives both shafts I! in rotation. The grinding chamber I2 is provided with an inlet chut 22 above the rolls I6, and an outlet chute 23 below the said rolls. The outlet chute covers the entire area of the bottom of the chamber I2 and is provided with suitable bearings 25 for the shafts I! for the purpose of preventing the material being treated from impeding the lower gears 20.

3 In the operation of this adaptation of my invention, th material to be treated enters the grinding chamber I2 through the chute 22, and

- falls down onto the rolls I6. If the rolls I6 were not being rotated, the material would simply drop down through the spaces (see Figure 1) between the hypocycloid and the side walls of the shell. However, when the rolls are rotated, the material being treated is carried around by the rolls and either forced outwardly by centrifugal force to pass between the epicycloid and the shell wall or forced in between the rolls. Thus, by regulating the rotational velocity of the rolls, and the rate of passage of the material through the chamber, the grinding action can be increased and the number of passes a given particle will make between the rolls can be controlled;

When grinding is commenced, the upper tapered portions of the rolls serve to disintegrate large particles and prepare them for further disintegration by the lower, more closely spaced portions of the rolls, and due to the cycloidal form of the rolls, the angles of divergence of the surfaces leading up to the narrowest points between the rolls and shell or the rolls themselves will be much smaller than such angles between cylindrical rolls of the same diameter. these rolls provide a greater grinding leverage and are capable of exerting greater force with less consumption of power than comparable cylindrical rolls. Furthermore, it will be seen that grinding can be done with this adaptation of my invention on a continuous basis.

While certain minor variations of my invention may become readily apparent to those skilled in the art, it is not intended to limit'the invention to the specific embodiments herein shown, but rather to measure it by the scope of the claims appended.

Having thus disclosed my invention and described in detail illustrative embodiments thereof, what I claim as new and desire to secure b Letters Patent of the United States is:

1. A grinding or dispersing mill adapted for handling material by a continuous process comprising walls forming a grinding chamber, two operatively associated circumferentially cycloidal rolls of substantially identical cross sectional contour, said rolls being mounted for rotation in geared relationship about parallel substantially vertical with the epicycloid of one roll fitting into the hypocycloid of the other roll, the upper ends of the said rolls being tapered, means for admitting material to be treated into the grinding chamber adjacent to the said tapered end of the said rolls, and means for recovering the'said material at the other end of the said chamber,'

said grinding chamber having walls closely surrounding the lower untapered portions of the rolls and spaced only by grinding clearance from the epicycloidal extremities thereof.

2. A grinding or dispersing mill adapted for handling material by a continuous process having in combination walls forming a grinding chamber, circumferentially cycloidal rolls operatively associated for disposition in parallel'substantially Vertical relationship, the said cycloidal Consequently,

5 rolls being tapered at one end, means for passing material to be treated through the said chamber so as to pass along the rolls from the tapered end thereof, the rolls being constructed to maintain a fixed distance from each other except at their tapered portions when rotated in opposite directions at the same rotational velocity, and the walls of the chamber being spaced from the widest points of said rolls only by the said fixed distance.

.3. A grinding machine comprising a pair of elongated circumferentially cycloidal rolls disposed substantially vertically on parallel axes having grinding clearance therebetween and tapering from closely interfitting end portions, walls forming a straight-sided grinding chamber closely surrounding the interfitting ends of the rolls and in grinding clearance therewith, means for rotating the rolls, said rolls having the larger ends of the rolls lower than the smaller ends, means for admitting material at the upper end of the chamber, and means for discharging material at the lower end thereof.

COLE D. NEFF.

REFERENCES CITED The following references are of record ;-in-'the file of this patent:

UNITED STATES PATENTS Number Name Date 45,222 Buchanan Nov. 29,1864 996,958 Wallick July 4, 1911 1,044,832 Wall Nov. 19, 1912 1,110,218 Mayer Sept. 8, 1914 1,216,383 West Feb. 20, 1917 1,681,920 Baccellieri Aug. 28, 1928 2,093,606 Goll Sept. 21, 1937 2,170,303 Helstrup Aug. 22, 19 39 2,309,594 Hutchings Jan. 26, 1943 FOREIGN PATENTS Number Country Date 84,040 Germany Mar. 30,1895 24,154 Great Britain Feb. 26, 1914 303,491 Germany Nov. 11, 1915 

